Liquid Chromatographic Determination of Methylene Blue and Its Metabolites in Milk

1992 ◽  
Vol 75 (5) ◽  
pp. 796-800 ◽  
Author(s):  
Robert K Munns ◽  
David C Holland ◽  
José E Roybal ◽  
John G Meyer ◽  
Jeffrey A Hurlbut ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Solid Phase ◽  
Chromatographic Determination ◽  
Lactating Cows ◽  
Azure B ◽  
Leuco Form ◽  
Fortified Milk ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

Abstract A method is described for the liquid chromatographic (LC) determination of trace levels of methylene blue (MB) and its metabolites in milk. The cleanup involves protein precipitation with acetonitrile, extraction into chloroform of MB and its metabolites (azure A [AZA], azure B [AZB], and azure C [AZC]), extraction by chloroform of thionin at pH 10, and solid-phase extraction on a disposable carboxylic acid column. LC separation and quantitation are performed with an isocratic acetonitrile-acetate buffer mobile phase on a cyano column. Average recoveries (5-20 ppb levels) of MB, AZA, AZB, and thionin from fortified milk were 83.2,60.0, 84.4, and 22.5%, respectively. Some incurred MB metabolites in milk are bound organically to a fraction of the milk substrate, whereas others are free demethylated forms of MB. Analysis of milk collected 8 h after administration of MB contained the following average levels (n = 6) of free MB and metabolites: MB, 31.0 ppb; AZA, 21.3 ppb; and AZB, 54.1 ppb. Depletion of free MB and metabolites AZA and AZB from milk after administration of MB to lactating cows occurred in less than 40 h. Metabolites of MB that formed complexes with organic compounds were hydrolyzed in part to the free forms. The leuco form of MB cou

Matrix Solid-Phase Dispersion (MSPD) Isolation and Liquid Chromatographic Determination of Oxytetracycline, Tetracycline, and Chlortetracycline in Milk

1990 ◽  
Vol 73 (3) ◽  
pp. 379-384 ◽  
Author(s):  
Austin R Long ◽  
Lily C Hsieh ◽  
Marsha S Malbrouh ◽  
Charles R Short ◽  
Steven A Barker
Keyword(s):  
Solid Phase ◽  
Correlation Coefficients ◽  
Chromatographic Determination ◽  
Average Percentage ◽  
Phase Dispersion ◽  
Fortified Milk ◽  
Photodiode Array ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

Abstract A multlresldue method for the isolation and liquid chromatographic determination of oxytetracycline (OTC), tetracycline (TC), and chlortetracycllne (CTC) antibiotics In milk Is presented. Blank and tetracycline (OTC, TC, and CTC) fortified milk samples (0.5 mL) were blended with octadecylsllyl (C18, 40 /an, 18% load, endcapped, 2 g) derivatized silica packing material containing 0.05 g each of oxalic acid and dlsodlum ethylenedlamlnetetraacetlc. A column made from the C18/milk matrix was first washed with hexane (8 mL), following which the tetracyclines were eluted with ethyl acetate-acetonltrlle (1 + 3; v/v). The eluate contained tetracycline analytes that were free from Interfering compounds when analyzed by liquid chromatography with UV detection (photodiode array, 365 nm). Correlation coefficients of standards curves for Individual tetracycline isolated from fortified samples were linear (from 0.982 ± 0.009 to 0.996 ± 0.004) with average percentage recoveries from 63.5 to 93.3 for the concentration range (100,200,400,800,1600, and 3200 ng/ mL) examined. The Inter-assay variability ranged from 8.5 ± 2.4% to 20.7 ± 13.0% with an Intra-assay variability of 1.0- 9.3%.

scholarly journals High-performance liquid chromatographic determination of famotidine in human plasma using solid-phase column extraction

2003 ◽  
Vol 68 (11) ◽  
pp. 883-892 ◽  
Author(s):  
Dragica Zendelovska ◽  
Trajce Stafilov
Keyword(s):  
Human Plasma ◽  
High Performance ◽  
Solid Phase ◽  
Internal Standard ◽  
Chromatographic Determination ◽  
High Performance Liquid Chromatographic ◽  
Water Ph ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

A rapid, specific and sensitive high-performance liquid chromatographic method for the determination of famotidine in human plasma has been developed. Famotidine and the internal standard were chromatographically separated from plasma components using a Lichrocart Lichrospher 60 RP select B cartridge for solid-phase separation with a mobile phase composed of 0.1 % (v/v) triethylamine in water (pH 3) and acetonitrile (92:8, v/v). UV detection was set at 270 nm. The calibration curve was linear in the concentration range of 10.0 ? 350.0 ng mL-1. The method was implemented to monitor the famotidine levels in patient samples.

Rapid Extraction and Cleanup for Liquid Chromatographic Determination of Domoic Acid in Unsalted Seafood

1995 ◽  
Vol 78 (2) ◽  
pp. 543-554 ◽  
Author(s):  
Michael A Quilliam ◽  
Mie Xie ◽  
William R Hardstaff
Keyword(s):  
Domoic Acid ◽  
Dynamic Range ◽  
Solid Phase ◽  
Chromatographic Determination ◽  
Single Step ◽  
Shellfish Poisoning ◽  
Rapid Extraction ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

Abstract Domoic acid is the toxin responsible for incidents of amnesic shellfish poisoning. A rapid extraction and cleanup for the liquid chromatographic determination of domoic acid in unsalted seafood is reported. The method uses a single-step extraction with 50% aqueous methanol and a selective cleanup and preconcentration with strong-anion exchange, solid-phase extraction. Determination is performed by liquid chromatography with ultraviolet absorbance detection. The detection limit was 20–30 ng/g. Recoveries of 93% were achieved from 0.2 to 20 μg/g in mussel tissues. The method gave a precision of less than 3% for concentrations greater than 2 μg/g and less than 6% at 0.2 μg/g. A linear dynamic range of 104 can be achieved. The method was successfully applied to a variety of seafood products, including mussels, razor clams, crabs, and anchovies.

scholarly journals Liquid Chromatographic Determination of Acriflavine and Proflavine Residues in Channel Catfish Muscle

1997 ◽  
Vol 80 (3) ◽  
pp. 486-490
Author(s):  
Steven M Plakas ◽  
Kathleen R El Said ◽  
Edward L E Jester ◽  
F Aladar Bencsath ◽  
William L Hayton
Keyword(s):  
Channel Catfish ◽  
Solid Phase ◽  
Water Concentration ◽  
Chromatographic Determination ◽  
Relative Standard ◽  
Waterborne Exposure ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic ◽  
Poor Absorption

Abstract A liquid chromatographic (LC) method was developed for determination of acriflavine (ACR) and proflavine (PRO) residues in channel catfish muscle. Residues were extracted with acidified methanol solution, and extracts were cleaned up with Ci& solid-phase extraction columns. Residue concentrations were determined on an LC cyano column, with spectrophotometric detection at 454 nm. Catfish muscle was individually fortified with ACR (purified from commercial product) and PRO at concentrations of 5,10,20, 40, and 80 ppb (5 replicates per level). Mean recoveries from fortified muscle at each level ranged from 86 to 95%, with relative standard deviations (RSDs) of 2.5 to 5.7%. The method was applied to incurred residues of ACR and PRO in muscle after waterborne exposure of channel catfish to commercial acriflavine (10 ppm total dye for 4 h). RSDs for incurred residues of ACR and PRO were in the same range as those for fortified muscle. Low residue concentrations (<1 % of exposure water concentration) suggested poor absorption of ACR and PRO in catfish.

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